This invention relates to an image forming apparatus such as a full-color copying machine or color printer.
Conventionally, as an image forming apparatus for outputting a color image, there is known a so-called 4-series tandem type full-color copying machine having four image forming units arranged side by side along the conveyer belt, for forming toner images of respective colors of yellow (Y), magenta (M), cyan (C) and black (B) based on color-separated image signals.
The image forming unit of each color has a photo-sensitive drum in rolling-contact with the conveyer belt, a charging device for charging the drum surface to a preset potential, an exposure device for exposing the drum surface to form an electrostatic latent image, a developing device for supplying toner to the electrostatic latent image on the drum surface to develop the same, and a transfer device for transferring the developed toner image on recording paper which is fed while being attracted to the conveyer belt. Then, the recording paper which is attracted to the conveyer belt is fed through the four image forming units, toner images of respective colors are transferred on the recording paper in a superposing manner, it is fed to the fixing device and the images of respective colors are fixed on the recording paper to form a color image.
In the above-described 4-series tandem type full-color copying machine using a DD motor (direct drive motor) for driving the photosensitive drum, the diameters of the four photosensitive drums are made equal to each other, a multi-pulse encoder is used to enhance the rotation precision, and angular speed settling control using the pulse signal is adopted.
On the other hand, the frequency of use of black among the four colors by the user in a monochrome mode is high. Therefore, for the high-speed operation of monochrome copying and long service life of the photosensitive drum, a method for increasing the diameter of the photosensitive drum for black is considered. In this case, since the diameters of the photosensitive drums are different, synchronization cannot be attained by using the conventional motor control with the angular speed kept constant as it is. The direct drive is given up and a method for changing the angular speed by use of gears can be provided, but in this case, it will be subject to a variation in rotation due to the precision of the gears.
Therefore, at present, even when the diameter of the photosensitive drum for black is made larger, the same encoder pulse number is used. For this reason, the circumferential speed of the photosensitive drum for black becomes higher in comparison with the other photosensitive drums and a difference in speed at the contact portions with the conveyer belt occurs. As a result, there occurs a defect that the service lives of the photosensitive drums and the belt are shortened and the image distortion occurs.
Further, in a case where the diameters of the respective photosensitive drums are the same, it is required to make fine adjustment and rotate the respective photosensitive drums at the constant circumferential speed.
An object of this invention is to avoid a defect that the service lives of the photosensitive drums and the belt are shortened and the image distortion occurs, make it possible to increase the diameter of the photosensitive drum for black in comparison with the photosensitive drums for the other colors and attain the high-speed operation of the monochrome copying and the long service life of the photosensitive drum for black.
An object of this invention is to make it possible to finely adjust a small difference of the circumferential speed by changing the pulse of a reference clock so as to rotate the respective photosensitive drums at a constant circumferential speed in a case where the diameters of the respective photosensitive drums are the same.
An object of this invention is to make it possible to roughly adjust a small difference of the circumferential speed by changing an encoder pulse and finely adjust a difference between the peripheral speeds (circumferential speeds) caused by a variation in the diameters of the respective photosensitive drums by changing the pulse of a reference clock so as to rotate the respective photosensitive drums at a constant circumferential speed in a case where the diameters of the respective photosensitive drums are the same.
In order to attain the above object, this invention provides an image forming apparatus comprising a feeding section for feeding a recording medium; a first image forming unit respectively including a first image carrying body provided along the feeding section and arranged in contact with the feeding section, a first latent image forming section for forming a latent image on the first image carrying body, a first developing section for supplying toner of first color to the latent image formed on the first image carrying body by the first latent image forming section to develop the same, and a first transfer section for transferring the toner image developed by the first developing section on the recording medium fed by the feeding section; a second image forming unit respectively including a second image carrying body having a larger diameter than the first image carrying body, provided along the feeding section in a succeeding stage of the first image forming unit and arranged in contact with the feeding section, a second latent image forming section for forming a latent image on the second image carrying body, a second developing section for supplying toner of second color to the latent image formed on the second image carrying body by the second latent image forming section to develop the same, and a second transfer section for transferring the toner image developed by the second developing section on the recording medium fed by the feeding section; a first rotating section for rotating the first image carrying body; a second rotating section for rotating the second image carrying body; a first control section for controlling rotation of the first rotating section at the rate of rotation based on the diameter of the first image carrying body; a second control section for controlling rotation of the second rotating section at the rate of rotation based on the diameter of the second image carrying body; and a fixing section provided along the feeding section in a succeeding stage of the second image forming unit, for fixing the toner image transferred on the recording medium; and characterized in that the circumferential speeds of the first, second image carrying bodies are made equal to each other.
Further, this invention provides an image forming apparatus comprising a feeding section for feeding a recording medium; a first image forming unit respectively including a first image carrying body provided along the feeding section and arranged in contact with the feeding section, a first latent image forming section for forming a latent image on the first image carrying body, a first developing section for supplying toner of first color to the latent image formed on the first image carrying body by the first latent image forming section to develop the same, and a first transfer section for transferring the toner image developed by the first developing section on the recording medium fed by the feeding section; a second image forming unit respectively including a second image carrying body having a larger diameter than the first image carrying body, provided along the feeding section in a succeeding stage of the first image forming unit and arranged in contact with the feeding section, a second latent image forming section for forming a latent image on the second image carrying body, a second developing section for supplying toner of second color to the latent image formed on the second image carrying body by the second latent image forming section to develop the same, and a second transfer section for transferring the toner image developed by the second developing section on the recording medium fed by the feeding section; a first rotating section for rotating the first image carrying body; a second rotating section for rotating the second image carrying body; a first output section for outputting an encode pulse with a preset number of pulses for one revolution based on a first encoder provided on the rotating shaft of the first rotating section; a second output section for outputting an encode pulse with n times (n=the diameter of the second image carrying body÷the diameter of the first image carrying body) the preset number of pulses for one revolution based on a second encoder provided on the rotating shaft of the second rotating section; a first control section for controlling rotation of the first rotating section at the rate of rotation based on the encode pulse from the first output section; a second control section for controlling rotation of the second rotating section at the rate of rotation based on the encode pulse from the second output section; and a fixing section provided along the feeding section in a succeeding stage of the second image forming unit, for fixing the toner image transferred on the recording medium; and characterized in that the circumferential speeds of the first, second image carrying bodies are made equal to each other.
Further, this invention provides an image forming apparatus comprising a feeding section for feeding a recording medium; a first image forming unit respectively including a first image carrying body provided along the feeding section and arranged in contact with the feeding section, a first latent image forming section for forming a latent image on the first image carrying body, a first developing section for supplying toner of first color to the latent image formed on the first image carrying body by the first latent image forming section to develop the same, and a first transfer section for transferring the toner image developed by the first developing section on the recording medium fed by the feeding section; a second image forming unit respectively including a second image carrying body having a larger diameter than the first image carrying body, provided along the feeding section in a succeeding stage of the first image forming unit and arranged in contact with the feeding section, a second latent image forming section for forming a latent image on the second image carrying body, a second developing section for supplying toner of second color to the latent image formed on the second image carrying body by the second latent image forming section to develop the same, and a second transfer section for transferring the toner image developed by the second developing section on the recording medium fed by the feeding section; a first rotating section for rotating the first image carrying body; a second rotating section for rotating the second image carrying body; a first output section for outputting an encode pulse with a preset number of pulses for one revolution based on a first encoder provided on the rotating shaft of the first rotating section; a second output section for outputting an encode pulse with a preset number of pulses for one revolution based on a second encoder provided on the rotating shaft of the second rotating section; converting means for converting an encode pulse from the second output section to a multiplied or frequency-divided pulse based on a difference between the diameters of the first and second image carrying bodies; a first control section for controlling rotation of the first rotating section at the rate of rotation based on the encode pulse from the first output section; a second control section for controlling rotation of the second rotating section at the rate of rotation based on the pulse from the converting means; and a fixing section provided along the feeding section in a succeeding stage of the second image forming unit, for fixing the toner image transferred on the recording medium; and characterized in that the circumferential speeds of the first, second image carrying bodies are made equal to each other.
Further, this invention provides an image forming apparatus comprising a feeding section for feeding a recording medium; a first image forming unit respectively including a first image carrying body provided along the feeding section and arranged in contact with the feeding section, a first latent image forming section for forming a latent image on the first image carrying body, a first developing section for supplying toner of first color to the latent image formed on the first image carrying body by the first latent image forming section to develop the same, and a first transfer section for transferring the toner image developed by the first developing section on the recording medium fed by the feeding section; a second image forming unit respectively including a second image carrying body having a larger diameter than the first image carrying body, provided along the feeding section in a succeeding stage of the first image forming unit and arranged in contact with the feeding section, a second latent image forming section for forming a latent image on the second image carrying body, a second developing section for supplying toner of second color to the latent image formed on the second image carrying body by the second latent image forming section to develop the same, and a second transfer section for transferring the toner image developed by the second developing section on the recording medium fed by the feeding section; a first rotating section for rotating the first image carrying body; a second rotating section for rotating the second image carrying body; a first output section for outputting an encode pulse with a preset number of pulses for one revolution based on a first encoder provided on the rotating shaft of the first rotating section; a second output section for outputting an encode pulse with a preset number of pulses for one revolution based on a second encoder provided on the rotating shaft of the second rotating section; a third output section for outputting a reference clock for rotating the first, second rotating sections at the preset rates of rotation; converting means for converting the reference clock from the third output section to a multiplied or frequency-divided pulse based on a difference between the diameters of the first and second image carrying bodies; a first control section for controlling rotation of the first rotating section at the rate of rotation based on the encode pulse from the first output section and the reference clock from the third output section; a second control section for controlling rotation of the second rotating section at the rate of rotation based on the encode pulse from the second output section and the pulse from the converting means; and a fixing section provided along the feeding section in a succeeding stage of the second image forming unit, for fixing the toner image transferred on the recording medium; and characterized in that the circumferential speeds of the first, second image carrying bodies are made equal to each other.
Further, this invention provides an image forming apparatus comprising a feeding section for feeding a recording medium; a first image forming unit respectively including a first image carrying body provided along the feeding section and arranged in contact with the feeding section, a first latent image forming section for forming a latent image on the first image carrying body, a first developing section for supplying toner of first color to the latent image formed on the first image carrying body by the first latent image forming section to develop the same, and a first transfer section for transferring the toner image developed by the first developing section on the recording medium fed by the feeding section; a second image forming unit respectively including a second image carrying body having the same diameter as the first image carrying body, provided along the feeding section in a succeeding stage of the first image forming unit and arranged in contact with the feeding section, a second latent image forming section for forming a latent image on the second image carrying body, a second developing section for supplying toner of second color to the latent image formed on the second image carrying body by the second latent image forming section to develop the same, and a second transfer section for transferring the toner image developed by the second developing section on the recording medium fed by the feeding section; a first rotating section for rotating the first image carrying body; a second rotating section for rotating the second image carrying body; a first output section for outputting an encode pulse with a preset number of pulses for one revolution based on a first encoder provided on the rotating shaft of the first rotating section; a second output section for outputting an encode pulse with a preset number of pulses for one revolution based on a second encoder provided on the rotating shaft of the second rotating section; a third output section for outputting a reference clock for rotating the first, second rotating sections at the preset rates of rotation; converting means for converting the reference clock from the third output section to a multiplied or frequency-divided pulse based on a difference between the circumferential speed of the first image carrying body and the circumferential speed of the second image carrying body; a first control section for controlling rotation of the first rotating section at the rate of rotation based on the encode pulse from the first output section and the reference clock from the third output section; a second control section for controlling rotation of the second rotating section at the rate of rotation based on the encode pulse from the second output section and the pulse from the converting means; and a fixing section provided along the feeding section in a succeeding stage of the second image forming unit, for fixing the toner image transferred on the recording medium; and characterized in that the circumferential speeds of the first, second image carrying bodies are made equal to each other.
Further, this invention provides an image forming apparatus comprising a feeding section for feeding a recording medium; a first image forming unit respectively including a first image carrying body provided along the feeding section and arranged in contact with the feeding section, a first latent image forming section for forming a latent image on the first image carrying body, a first developing section for supplying toner of first color to the latent image formed on the first image carrying body by the first latent image forming section to develop the same, and a first transfer section for transferring the toner image developed by the first developing section on the recording medium fed by the feeding section; a second image forming unit respectively including a second image carrying body having a diameter larger than the first image carrying body, provided along the feeding section in a succeeding stage of the first image forming unit and arranged in contact with the feeding section, a second latent image forming section for forming a latent image on the second image carrying body, a second developing section for supplying toner of second color to the latent image formed on the second image carrying body by the second latent image forming section to develop the same, and a second transfer section for transferring the toner image developed by the second developing section on the recording medium fed by the feeding section; a first rotating section for rotating the first image carrying body; a second rotating section for rotating the second image carrying body; a first output section for outputting an encode pulse with a preset number of pulses for one revolution based on a first encoder provided on the rotating shaft of the first rotating section; a second output section for outputting an encode pulse with a preset number of pulses for one revolution based on a second encoder provided on the rotating shaft of the second rotating section; a third output section for outputting a reference clock for rotating the first, second rotating sections at the preset rates of rotation; converting means for converting the reference clock from the third output section to a multiplied or frequency-divided pulse based on a difference between the circumferential speed of the first image carrying body and the circumferential speed of the second image carrying body; a first control section for controlling rotation of the first rotating section at the rate of rotation based on the encode pulse from the first output section and the reference clock from the third output section; a second control section for controlling rotation of the second rotating section at the rate of rotation based on the encode pulse from the second output section and the pulse from the converting means; and a fixing section provided along the feeding section in a succeeding stage of the second image forming unit, for fixing the toner image transferred on the recording medium; and characterized in that the circumferential speeds of the first, second image carrying bodies are made equal to each other.
Further, this invention provides an image forming apparatus comprising a feeding section for feeding a recording medium; a first image forming unit respectively including a first image carrying body provided along the feeding section and arranged in contact with the feeding section, a first latent image forming section for forming a latent image on the first image carrying body, a first developing section for supplying toner of first color to the latent image formed on the first image carrying body by the first latent image forming section to develop the same, and a first transfer section for transferring the toner image developed by the first developing section on the recording medium fed by the feeding section; a second image forming unit respectively including a second image carrying body having a larger diameter than the first image carrying body, provided along the feeding section in a succeeding stage of the first image forming unit and arranged in contact with the feeding section, a second latent image forming section for forming a latent image on the second image carrying body, a second developing section for supplying toner of second color to the latent image formed on the second image carrying body by the second latent image forming section to develop the same, and a second transfer section for transferring the toner image developed by the second developing section on the recording medium fed by the feeding section; a first rotating section for rotating the first image carrying body; a second rotating section for rotating the second image carrying body; a first output section for outputting an encode pulse with a preset number of pulses for one revolution based on a first encoder provided on the rotating shaft of the first rotating section; a second output section for outputting an encode pulse with a preset number of pulses for one revolution based on a second encoder provided on the rotating shaft of the second rotating section; first converting means for converting the encode pulse from the second output section to a multiplied or frequency-divided pulse based on a difference between the diameters of the first, second image carrying bodies; a third output section for outputting a reference clock for rotating the first, second rotating sections at the preset rates of rotation; second converting means for converting the reference clock from the third output section to a multiplied or frequency-divided pulse based on a difference between the circumferential speed of the first image carrying body and the circumferential speed of the second image carrying body; a first control section for controlling rotation of the first rotating section at the rate of rotation based on the encode pulse from the first output section and the reference clock from the third output section; a second control section for controlling rotation of the second rotating section at the rate of rotation based on the pulse from the first converting means and the pulse from the second converting means; and a fixing section provided along the feeding section in a succeeding stage of the second image forming unit, for fixing the toner image transferred on the recording medium; and characterized in that the circumferential speeds of the first, second image carrying bodies are made equal to each other.
Further, this invention provides an image forming apparatus comprising a feeding section for feeding a recording medium; a first image forming unit respectively including a first image carrying body provided along the feeding section and arranged in contact with the feeding section, a first latent image forming section for forming a latent image on the first image carrying body, a first developing section for supplying toner of first color to the latent image formed on the first image carrying body by the first latent image forming section to develop the same, and a first transfer section for transferring the toner image developed by the first developing section on the recording medium fed by the feeding section; a second image forming unit respectively including a second image carrying body having the same diameter as the first image carrying body, provided along the feeding section in a succeeding stage of the first image forming unit and arranged in contact with the feeding section, a second latent image forming section for forming a latent image on the second image carrying body, a second developing section for supplying toner of second color to the latent image formed on the second image carrying body by the second latent image forming section to develop the same, and a second transfer section for transferring the toner image developed by the second developing section on the recording medium fed by the feeding section; a first rotating section for rotating the first image carrying body; a second rotating section for rotating the second image carrying body; a first output section for outputting an encode pulse with a preset number of pulses for one revolution based on a first encoder provided on the rotating shaft of the first rotating section; a second output section for outputting an encode pulse with a preset number of pulses for one revolution based on a second encoder provided on the rotating shaft of the second rotating section; first converting means for converting the encode pulse from the second output section to a multiplied or frequency-divided pulse based on a difference between the circumferential speed of the first image carrying body and the circumferential speed of the second image carrying body; a third output section for outputting a reference clock for rotating the first, second rotating sections at the preset rates of rotation; second converting means for converting the reference clock from the third output section to a multiplied or frequency-divided pulse based on a variation in the peripheral speed of the first image carrying body; third converting means for converting the reference clock from the third output section to a multiplied or frequency-divided pulse based on a variation in the peripheral speed of the second image carrying body; a first control section for controlling rotation of the first rotating section at the rate of rotation based on the encode pulse from the first output section and the pulse from the second converting means; a second control section for controlling rotation of the second rotating section at the rate of rotation based on the pulse from the first converting means and the pulse from the third converting means; and a fixing section provided along the feeding section in a succeeding stage of the second image forming unit, for fixing the toner image transferred on the recording medium; and characterized in that the circumferential speeds of the first, second image carrying bodies are made equal to each other.